Those who are not accustomed to the “language” of Tibetan Buddhist images are often surprised to see the wrathful deities for the first time.
One category of these is the herukas, a class of Vajrayana deities such as Chakrasamvara that is semi-wrathful with intimidating, even terrible, features. They are represented as partially nude with an upper garment of human skin and a tiger skin around their hips. They have a 5-skull headdress and carry bone rosaries, a staff or trident and a damaru (pellet drum) like the Hindu god, Shiva. Herukas are described in Tibetan books as beautiful, heroic, awe-inspiring, stern and majestic.
The heruka (tRak-thung) is a masculine deity, wrathful or semiwrathful, who represents the dynamic of compassion and skillful means in Tibetan tantra. The heruka traces its origin to the same pre-Buddhist traditions of India as the dakini, in the retinues of wrathful Siva or Mahakala in which he served as terrifying demon.
Heruka literally means “blood-drinker,” and in a tantric Buddhist setting this refers to drinking the blood of self-cherishing, doubt, and dualistic confusion. The tantric interpretation of the term heruka derives a further meaning: his nature is beyond conventional cause and effect, existence, and duality. He is the ultimate expression of the radiantly selfless qualities of the mind. Having drunk the blood, the heruka experiences bliss. He is fearlessly at home in the charnel ground, and under his gaze it is no longer merely charnel — it is a palace.
“The heruka is depicted with nine classical moods (Kartap gu) which gives clues about his manifestation. He is said to be charming, with dazzling ornaments; brave, posing and strutting; threatening, with rolling eyes and a wrathful grimace; laughing, a raucous “ha ha”; fierce, with laughter that mocks, “hi, hi, hum, phat”; fearsome, grinding his teeth and brandishing a weapon; compassionate; with bloodshot eyes and radiant skin; outrageous, with gaping mouth and clicking tongue; and peaceful, gently gazing at the tip of his nose. The heruka embodies the mountain-like presence of the enlightened masculine principle in Vajrayana Buddhism, with its range of fierce, hearty, and gentle qualities.”